Strand material, such as glass, nylon, orlon, cotton, and other like strands, is typically collected by winding the strand material around a rotating surface such as a collet. In the case of glass strands, glass filaments are typically attenuated through orifices or bushing tips at the bottom of a heated bushing containing molten glass. The filaments are then passed across the application surface of an applicator where they are coated with a binder and/or size. The filaments are subsequently gathered into a unified strand by a gathering shoe, which is typically a grooved cylinder formed of material such as graphite. Alternatively, the applying and gathering steps may be accomplished by a single device, such as a pad applicator. The strand is then traversed across the face of a rotating spiral and wound on a rotating mandrel or collet as a forming package.
Several problems are encountered in the collection of glass strands in this manner. The rotating spiral wears due to the abrasion between its surfaces and the glass strands passing across it, necessitating frequent replacement of the spirals. Further, since this wear is not always uniform across the surfaces of the spiral, ridges and/or nicks in the surface of the spiral can often result. These ridges or nicks are locations where the glass strand may break out, thus necessitating a stoppage in what is desired to be a continuous process. Any nick or ridge on a spiral results in an even shorter life of the spiral than would normally be expected by uniform wear on its surface.
It would, therefore, be desirable to wind strand material, and especially glass strands, without the necessity of traversing the strands across the face of a rotating spiral prior to winding them on the rotating collet.
A second problem with winding glass strands is in the construction of the collet. In many applications, the collet, which is the rotating surface on which strands are collected, reciprocates along its axis under the rotating spiral to allow the strands to build up as a forming package across essentially the entire length of the collet. The weight of the collet itself along with that of the strands being wound thereon, which may themselves weigh up to about 125 pounds (56.63 kilograms) and more, places a great deal of strain on the bearings which hold the collet, especially as the collet is reciprocated to its outermost position away from the bearings, due to bending moment forces acting on the bearings. These bearings have often failed in the past due to the forces being exerted upon them. This requires shut down for bearing replacement in the collet and considerable lost time and maintenance expense.
It would also, therefore, be desirable to eliminate the necessity for reciprocating the collet below a rotating spiral.
In U.S. Pat. No. 3,115,312 a glass strand collecting apparatus is disclosed which has eliminated both the rotating spiral and the necessity of reciprocating the collet under a spiral or other traversing means. In this patent, the rotating collet is connected to a motor which supplies the rotational forces for it. The motor is mounted on a rotating cam to raise and lower both the motor and the collet through an included angle. As the collet rises and falls the strand is collected at various locations along its face to enable a generally cylindrical package to be formed along essentially the entire length of the collet.
A problem of the strand collection system of this patent lies in its geometry. As the collet rises and falls, the distance between the collet surface and the supply of strand, in this case the applicator pad surface, is variable, being shortened as the collet rises and being lengthened as the collet falls. This produces an uneven tension on the strand as it is being wound.
Uneven tension results in two deleterious effects to the strand. If severe enough, the tension variations will cause the strand to break, thus requiring restarts of the system and reduction in its overall productivity. Less noticeable, but as severe, is the problem of nonuniform strand quality due to uneven tension on the strand. The rotating collet winding the strand thereon produces the attenuative forces for drawing the filaments which form the strand from the bushing tips in the bushing. The amount of pull on the filaments is directly proportional to the tension exerted on the strand. Also, for a given bushing tip or orifice size, the diameter of the filaments being formed is dependent upon the pull given to the filaments and thus upon the tension on the strand. If the strand tension changes, as is continuously the result in this patent, the filament diameter will also continuously change, thus resulting in a low quality strand which is commercially unacceptable.
It is therefore desirable to collect strand material, and especially glass strands, with a constant level of tension being exerted on the strand.